Drought-Tracking Satellite to Blast Off This Month

Below:

Next story in Science

A new satellite expected to launch this month will improve
drought monitoring in the United States and around the world,
NASA scientists said Thursday (Jan. 8).

The Soil Moisture Active Passive (SMAP) satellite will provide
the best maps yet of soil
moisture levels from pole to pole, mission scientists said.
Soil moisture is one of the key factors in estimating drought
severity; it also influences local weather, adds to hazards such
as flooding, and plays a role in how plants
store and release carbon.

"I think the next couple of years are going to be very exciting
for Earth science," Dara Entekhabi, SMAP science team lead and an
environmental engineer at MIT, said Thursday during a NASA media
briefing.

Data from the satellite will track global soil moisture levels
for the top 2 inches (5 centimeters) of Earth's surface every two
to three days. For the first time, scientists will get a
bird's-eye view of drought patterns; for instance, they'll watch
where droughts begin and end, and how droughts spread across
large areas. The mission is planned to last three years, at a
cost of $916 million (including launch), but the instruments
could last several years longer, mission scientists said.
[ Dry
and Dying: Images of Drought ]

The SMAP satellite, which will be carried aloft by a Delta II
rocket, is scheduled to launch Jan. 29 from Vandenberg Air Force
Base in California.

Eyes on dry

The soil moisture maps will help farmers who depend on rain to
irrigate crops, the scientists said. However, the satellite can't
tell farmers whether a particular field is ready to plant — the
maps can't detail features as small as a typical farm plot. The
resolution will be about 6 miles (10 kilometers), according to
NASA.

Researchers will also examine links between soil moisture and
weather, such as rainfall and temperature. Soil moisture affects
the weather through evaporation, because when the sun's energy
bakes water out of the soil, it cools the surface — the same
cooling effect sweating has on the body, Entekhabi said.

The soil moisture maps could also help improve
flood warnings because forecasters will know how wet the
ground is before an intense storm. Less than 1 percent of Earth's
water is stored in soil — most is in the oceans and frozen in ice
— but soil moisture determines how much freshwater is in rivers
and lakes, Entekhabi said.

"It's a tiny amount, but it's rather important and very active,"
Entekhabi said.

The SMAP satellite's most prominent feature is its rotating mesh
antenna, which measures nearly 20 feet (6 meters) across — the
largest ever deployed in space. For launch, the antenna stows
into a nook the size of a tall trash can. Mounted on a long arm
like a giant beach umbrella, a motor spins the antenna at 14.6
revolutions per minute. A radar and radiometer complete the main
parts.

"The spacecraft looks somewhat like the tail wagging the dog with
this very large antenna," said Kent Kellogg, SMAP project manager
at NASA's Jet Propulsion Laboratory in Pasadena, California.

The radar beams microwaves at Earth, and the radiometer measures
Earth's emitted microwave radiation. Changes in the signals
indicate changes in soil moisture and whether the soil is
frozen.

SMAP was one of
five Earth observation satellites that NASA targeted for
blast off in 2014. The space agency's Orbiting Carbon
Observatory-2 satellite, Global Precipitation Measurement Core
Observatory and ISS-RapidScat all made it off the ground in 2014.
A scheduled Jan. 6 launch for the Cloud-Aerosol Transport mission
was scrubbed this week by SpaceX and is rescheduled for Saturday
(Jan. 10).

The five craft are intended to help NASA fill gaps in its
monitoring of the water, energy and carbon cycles, said Christine
Bonniksen, NASA program executive for SMAP.